A liquid crystal device is generally designed to have a liquid crystal sandwiched between a pair of substrates having a plurality of electrodes formed on surfaces thereof which are mutually opposed. A potential difference is produced between electrodes that are opposed and orthogonal to each other. Thus, the liquid crystal molecules are displaced. The liquid crystal device utilizing displacement of liquid crystal molecules has been widely adopted as an electro-optic device.
To be more specific, the liquid crystal device is placed between a pair of sheet polarizers arranged so that the axes of polarization thereof will be orthogonal to each other. At this time, an axis of absorption of one of the polarizers coincides with the direction of liquid crystal molecules. The liquid crystal molecules are displaced according to whether no voltage is applied to the liquid crystal device (light is transmitted) or a voltage is applied thereto (light is intercepted). A change in amount of light transmitted by the liquid crystal device is then detected.
Normally, belt-shaped electrodes arranged in a longitudinal direction are referred to as signal electrodes, and belt-shaped electrodes arranged in a lateral direction are referred to as scan electrodes. As mentioned above, a voltage signal is applied to the liquid crystal device while application of the signal is synchronized between each signal electrode and scan electrode. A potential difference between the signal electrode and scan electrode is utilized for driving liquid crystal molecules.
In this case, characteristic signals are produced by a driving IC chip or the like, and supplied to the signal electrodes and scan electrodes respectively. For supplying the signals to the electrodes, two methods, described below, have generally been adopted.
Specifically, one of the methods is the flip-chip bonding (chip-on-glass (COG) bonding for glass substrates) where output terminals of a driving IC chip and wiring electrodes led out from electrodes are electrically coupled with each other using a conductive adhesive, and the driving IC chip is mounted on one substrate. The other method is tape automated bonding (TAB) where a driving IC chip and electrodes on substrates are linked by a flexible printed circuit (FPC) and the driving IC chip is separated from the substrates.
In the case of the latter TAB, the FPC is used to link the substrates and driving IC chip. The density of lines of wiring is restricted because of a problem underlying bonding and manufacturing of the FPC. The compactness in design and the highness in density are therefore limited.
According to the former flip-chip bonding, the driving IC chip is bonded directly onto the electrodes or the wiring electrodes led out from the electrodes using the conductive adhesive. This solves the problem on the density of lines. Thus, a compact design and a high density are realized.
However, a major object of the flip-chip bonding is to realize the compact design and high density. Output pads located at the extreme tips of the wiring electrodes led out from the electrodes are bonded to the output terminals of the driving IC chip. The output pads are therefor packed at a very high density. Consequently, the wiring electrodes extending from pixels to the output pads get very thin and long. This brings about a variation in resistance among the wiring electrodes. An applied voltage therefore varies depending on the resistance. Consequently, there arises a problem that the appearance of a display screen becomes irregular.
The present invention especially attempts to solve the above problem underlying the flip-chip bonding.